A motor action results from a set of energetic processes leading a nerve signal via the spinal cord to effector organs. A partial or total lesion of the spinal cord leads to a degeneration of the nerve pathways that can no longer transmit signals to the spinal neurons beyond the lesion, which can lead to paralysis and also to an interruption of the upward pathways towards the brain, thereby leading to an abolition of sensation.
Understanding the mechanisms for conveying nerve signals along the spinal column is necessary in order to develop the most effective possible therapeutic treatments.
It is known that variability in the distribution of oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (Hb) can be observed from the blood vessels and capillaries irrigating the neural regions of the cortex and of the spinal column during cognitive or motor activity.
By relying on an optical imaging device that enables these variations in blood volume and oxygenation to be detected, it has been possible to study the neural tissues of the brain. Nevertheless, the technology used is of too great a size to be placed on some other portion of the body or to be implanted continuously in a vertebrate. Whereas trepanation suffices to gain access to brain tissue, gaining access to medullary tissue is more difficult and requires a laminectomy. Finally, the known optical imaging device mainly comprises optical fibers, and such fibers are difficult to use in the spinal cord since their shape makes it difficult for them to be integrated in simple manner in order to measure the hemodynamic response.
At present, the main means for studying the spinal cord as a whole thus remains magnetic resonance imaging (MRI) which enables the cord to be viewed and medullary tissues to be analyzed. Nevertheless, such study remains external, and neural activity perceived in the medullary tissues is scrambled and difficult to interpret from one patient to another.